In this paper I wish to show in detail clinical material, and how by using this we investigate the semantic distortion, and the use of linguistics as applied to investigating clinical psychoanalysis. In Part IV, I am referring to Freud's patient the "Rat Man'. Compliance with the requirements of the setting, that is, being punctual, associating freely or pretending to, does not mean that many of the patients we are going to discuss here may not put the psychoanalytic setting and language to the service of secret resistances and hidden pregenital pleasure. Perhaps it would be more adequate to say, of a certain type of resistance. But as it happens in the case of my patients illustrated in Parts II and III, we must investigate the meaning of the patients distorted notion of psychoanalytic treatment. This distorted notion we call semantic distortion. Some times it is an apparent formal response which hides another secret level of using the therapist. Sometimes, the apparent formal compliance with the fundamental rule and with the setting, does not prevent the patient from using speech, tenses of verbs, tone of voice, questions, etc. with purposes which are very different from those we know of as adult communication. We are interested in investigating this use of verbal and bodily communications in the service of resistance. In many cases this resistance may be subtle, insidious or hidden, that is to say, more disguised than or different from those described by Freud in some of his first papers as resistance against speaking, evoking memories, associating: all these are easily observable signs which help the therapist to be on the alert. We are interested in exploring the communicational approach, that is, what the messages and speech modalities of the patient are, what they convey and contain.